Crankshaft Position Sensor (CKPS)

CKPS monitors engine speed and piston position. CKPS is built into distributor on G20 and into a separate sensor mounted on front of engine on J30 and Q45. CKPS has a rotor plate and a wave-forming circuit. Rotor plate has 360 small (outer) slits to determine crankshaft position (one slit for each degree of sensor rotation). Rotor plate also has 4 (4-cylinder), 6 (V6) or 8 (V8) large inner slits at 180-degree (4-cylinder), 120-degrees (V6) or 90-degree (V8) intervals to determine engine speed. Inner slit for No. 1 cylinder is wider than the other inner slits to allow ECM to determine TDC for No. 1 cylinder.

When signal rotor plate passes space between a Light Emitting Diode (LED) and photo diode, slits in signal rotor plate alternately cut light that is sent to photo diode from LED. This causes a pulsating voltage, which is converted into an on-off pulse by wave-forming circuit, and sent to ECM. Q45 also has a sub-crankshaft position sensor that is used as back-up to CKPS. See SUB-CRANKSHAFT POSITION SENSOR.